In mobile telephony, there is a constant requirement to achieve ever-higher transmission speeds. Various technical standards have been created which have brought continued improvements in transmission methods. Thus in mobile telephony a distinction can be made, for example, between systems such as GSM (Global System for Mobile Communications), HSCSD (High Speed Circuit Switched Data), EDGE (Enhanced Data rates for GSM Evolution), UMTS (Universal Mobile Telecommunications System) and for example HSPA (High-Speed Packet Access). Here the UMTS method is referred to as a third generation technology.
Apart from this UMTS technology a further development, the Long Term Evolution (LTE) technology, is now on the horizon which will supersede or further develop UMTS. In this respect the LTE technology is also being referred to as the 3.9-generation, which thus in terms of its timing comes just before the fourth generation technologies, but which nevertheless compared to alternative technologies such as WiMAX should allow a comparatively cost-effective and “seamless”, and therefore evolutionary, further development from UMTS to LTE.
Here, as will be known, the LTE technology uses Orthogonal-Frequency-Division-Multiplexing methods (OFDM), which ultimately are based on FDM technology, that is Frequency-Division-Multiplexing. FDM is an instance of a telecommunications multiplexing method, with which several signals can be transmitted simultaneously distributed over multiple carriers, whereby the multiple carriers are assigned different frequencies. The orthogonal FDM method is also an instance of a multi-carrier modulation method, in which multiple orthogonal carrier signals are used for digital data transmission.
Furthermore, here the LTE technology is also based on the MIMO technology, for which antennas are used which take account of the Multiple-Input-Multiple-Output principle.
LTE technology is also characterized here, for example, by comparatively low latency periods, whereby voice services (VoIP) or for example also video telephony can be improved. So, for example, with the 4×4 MIMO technology a peak data rate of, for example, more than 300 Mbps can be achieved in the downlink. In the process the uplink still achieves a peak data rate of over 75 Mbps, if for example a single antenna is used.
In known mobile telephony networks, on the base station side as a rule antenna are used which mainly have one or two antenna systems for the transmit branch and more often than not two antenna systems for the receive branch. The term “antenna system” here can mean two separate antennas, or also a dual polarized antenna with two decoupled connections for the two polarization planes which are perpendicular to one another. In the case of reception therefore, a polarization diversity that improves the reception quality or also a so-called space diversity is or are present.
Conventional mobile telephony base stations normally comprise all the essential parts that are necessary for operating such a base station. In order to minimize additional losses both in the transmission and reception direction, however, a module referred to as a Remote Radio Head (RHH) which is separate from the radio server and remote from this, i.e. as a rule in the vicinity of the antenna on a mast, can be provided. This essentially takes care of transmission and reception amplification and modulation of the carrier with the I/Q-signals transmitted via the optical interface. Communication between the radio server and the remote radio head RRH provided separately from this and in the vicinity of the mast preferably takes place via an optical interface.
As already mentioned in the latest mobile radio standard generation, the use of antennas is envisaged which comprise radiator devices in various slots.
This opens up the possibility outlined at the outset of operating the antenna using the so-called MIMO technology. Here several data streams are transmitted both on the transmission side and the reception side via the transceiver unit to the different antenna systems.
This also means that both for MIMO operation of the base station and also when conventional remote radio heads (RHH) are used the number of transceiver units required increases. Even if several transceiver branches are combined in a single housing, normally the number of A/D converters, the number of signal conditioning modules and the number of reception amplifiers increase approximately linearly with the number of antenna systems used.
A transceiver module for operating a mobile telephony base station employing MIMO technology is, for example, known from EP 1 923 954 A1. In such examples, the base station is equipped with an antenna device which comprises n slots, in which in each case offset vertically to each other dual polarized radiators are arranged, which for example radiate with an alignment that is at a +45° or −45° angle to the horizontal (or the vertical). Via a transmission unit the various slot inputs of the antenna device each have a transmission signal fed to them, with furthermore a receiver unit being connected to the various outputs of the antenna slots. Both the transmission unit and the reception unit have a number of connections for this purpose which are connected with the various connections on the slots of the individual antenna devices.
A MIMO system, for example with two transmission and two reception antennas, is also known from EP 1 643 661 B1.
Technology herein provides an improved transceiver module for reception and transmission of mobile telephony signals with multiple transmit-receive branches. The module is preferably operated with a radio server on the base station side. The module is preferably positioned in the vicinity of the antenna, for example on an antenna mast or other antenna installation point.
With the solution according to the invention an unexpectedly high variability is created which takes account of different transmission-reception scenarios and different development possibilities and thus allows cost-effective adaptations to be made according to changes in the requirements situation.
The solution according to the invention is characterized, inter alia, in that with the signal conditioning by channel of the transmission signal for the individual channels separate power amplifiers are provided, whereby for the transmission and reception of the signals for each channel or at least for the majority of the channels associated duplex filters are provided. Here the invention assumes that at least four channels are created. The essence of the invention is that a controller device is provided, via which several or all of the power amplifiers, which are connected in several or all channels, can be operated in-phase relation or phase locked to each other. This allows the transmission signals amplified in the channels concerned to be synchronized and thus interconnected with each other and alternatively by means of the multiple duplex filters that are present the individual channels can also be operated separately with various signals. This allows a transmission signal with a higher transmission power to be radiated.
The variability according to the invention as well as the possibility for adaptation according to the invention to various altered operational states, to frequency bands to be transmitted, carrier frequencies and so on, is preferably achieved in that a switching matrix is provided, via which the transmission signals with a specifiable carrier frequency and power amplifiers connected downstream can be fed as required to the various antenna systems. Here, via the switching matrix provided according to the invention, it is possible, for example, to feed to at least four transmission devices (frequency carriers) four separate antenna devices (whereby the four separate antenna systems can also comprise two slots with several dual polarized radiator devices, in which therefore radiators are provided in each of the two antenna slots, which because of their polarization direction or polarization planes being perpendicular to one another are decoupled from one another). It is also possible, however, by means of the switching matrix provided in accordance with the invention, for example with four transmission channels (transmission frequency carriers) to interconnect two, three or all four transmission signals on a single antenna input, whereby on the basis of the interconnection a higher transmission power can be achieved on an output.
According to the invention, however, it is also provided that the phase angles of the signals which are fed to the amplifiers, which are assigned to the individual transmission channels, are coupled in a phase-locked manner.
Thus in the context of the invention it is possible for, for example, two UMTS channels to be inter connected with a virtual doubling of the antenna beam power or for GSM carrier frequencies to be interconnected and fed to a second separate antenna input, etc. As mentioned, it is possible for all four transmission signals to be interconnected on one antenna input or for example for various carrier frequencies for various channels to be provided which feed the transmission signals to the different antenna inputs. In so doing in subsequent upgrades of the mobile telephony base station as a whole, new developments can be taken into account and for example a new channel based on the LTE technology or a number of channels based on the LTE technology implemented.
Generally speaking, according to the invention at least one 4-channel version of a transceiver unit is built, which is equipped with a controllable matrix circuit and with which, as mentioned, the power amplifiers provided for the respective transmission branch can be coupled in a phase-locked manner in the transmission channel concerned. With this configuration, ultimately different standards can be supported. In addition a previously unanticipated variety of configuration possibilities results. For in the context of the invention various carriers can be transmitted via various branches, whereby two or more identical carriers can be interconnected on a single branch, i.e. on a single antenna input. This transceiver module is preferably created in a remote radio head (RHH) with the at least four transceiver units mentioned, which can also have additional advantages:                The at least four transceiver units can collectively use a high proportion of the signal conditioning. Thus, for example, a multiple ND converter can be provided, i.e. for example in a 4-channel design of the transceiver unit a 4×A/D converter can be used. Furthermore, for the up-mixing in the transmission branch of the respective channel and in the respective reception branches a phase-locked loop (PLL) with a common oscillator can be used, provided that the same carrier frequencies are involved. Ultimately the same applies equally to the use of an optical converter and the common power supply unit.        For linearization and amplification control, the multiple transmission branches can use the transmission signal, which is decoupled from the corresponding signal branch by means of a decoupling mechanism and can be used in a faster sequential order for linearization (DPD)        Also of advantage is the fact that according to the configuration selected, thus according to the transmission channels, the corresponding duplex filters suitable for this can be provided. Duplex filters may even be used which can be employed for different, i.e. various, frequencies or frequency ranges. For example, duplex filters or duplex separating filters with various dual frequency pairs would be conceivable which would be suitable, for example, for a 1,800 MHz range and for the UMTS range.        In addition in a normal expansion scenario a new network cannot always be envisaged, if initially with the existing four or more antenna systems only one conventional standard (for example a GSM standard or a UMTS standard) is to and can be operated, or if possibly subsequently one or more or even all of the channels are not to be converted to the LTE standard or subsequent technologies. In the context of the invention, here, for example with a 4-channel solution, initially a 2×MIMO technology can be applied, in which for example two channels at a time are interconnected, in order then later to convert to a 4× solution.        The advantage of interconnection is always that all the at least four channels provided can be utilized, even if, for example, at a given point in time only one or two transmission standards are to be applied. In such a case this leads to an increase in the transmission power, as mentioned.        
Finally, a high bandwidth range of the device can be achieved by the duplex filter comprising at least two transmission signal band-pass filters connected in parallel. These two filters can be interconnected differently on the input side. In order to achieve a higher bandwidth range, the power amplifiers can also combine individual power amplifiers for different frequency ranges connected in parallel.